COPENHAGEN — Modern prenatal advice often focuses on what expectant mothers should avoid—alcohol, tobacco, certain medications. But what about the everyday foods that make up a typical Western diet? A new study reveals that the standard Western diet during pregnancy—high in processed meats, sugars, and refined grains with low intake of fruits and vegetables—is significantly associated with neurodevelopmental disorders in children, particularly ADHD and autism.

In a society where fast food and ultra-processed options increasingly dominate our dietary landscape, these findings deliver a sobering message: what a mother eats during pregnancy may influence her child’s brain development and future mental health in profound ways previously underappreciated.

“The greater a woman’s adherence to a Western diet in pregnancy – high in fat, sugar, and refined products while low in fish, vegetables, and fruit—the greater the risk appears to be for her child developing ADHD or autism,” says lead author, Dr. David Horner in a statement.

The study, led by researchers from the Copenhagen Prospective Studies on Asthma in Childhood (COPSAC), analyzed data from 508 mother-child pairs, examining maternal dietary patterns at 24 weeks of pregnancy and then evaluating the children for neurodevelopmental disorders at age 10. The researchers validated their findings across three additional independent cohorts involving over 60,000 mother-child pairs through various methodologies, lending considerable weight to their conclusions.

Neurodevelopmental disorders like ADHD and autism affect millions of children worldwide. In 2020, Danish registries reported that 5.9% of males and 3% of females developed ADHD during childhood and adolescence, while 4.3% of males and 1.8% of females received autism diagnoses. These statistics align with global estimates of around 5.9% for ADHD and up to 1.1% for autism.

How Western Diet Affects Child Development

The researchers employed a data-driven approach to identify dietary patterns from a food frequency questionnaire completed by mothers at 24 weeks of pregnancy. The analysis revealed two primary patterns: a “varied dietary pattern” that simply reflected overall food variety, and a “western dietary pattern” characterized by high consumption of processed meats, refined grains, high-energy drinks, and animal fats, combined with low intake of fruits, vegetables, fish, and whole grains.

After controlling for numerous factors including pre-pregnancy BMI, social circumstances, child sex, birth weight, gestational age, smoking during pregnancy, antibiotic use, pre-eclampsia, and the child’s own dietary pattern at age 10, the findings were striking. A Western dietary pattern during pregnancy was significantly associated with any neurodevelopmental disorder diagnosis (53% increased odds), ADHD (66% increased odds), and autism (122% increased odds).

Even moderate shifts along this dietary spectrum were associated with markedly increased risk. As Dr. Horner explains, “slight deviations towards a more Western diet were linked to a 66% increased risk of ADHD and a 122% increased risk of autism. However, this also presents an opportunity: even small dietary adjustments away from a Western pattern could potentially reduce the risk of neurodevelopmental disorders.”

Biological Evidence Through Blood Analysis

To validate these findings, the researchers turned to maternal blood samples collected during pregnancy and identified 43 metabolites—biological markers in the blood—associated with the Western dietary pattern. Fifteen of these metabolites were found to mediate the relationship between the Western diet and neurodevelopmental outcomes.

“We found that 15 of these 43 metabolites were particularly linked to the increased risk of ADHD. Many of these metabolites are derived from dietary intake and play key roles in regulating inflammation and oxidative stress—factors believed to be critical in early neurodevelopment,” says Dr. Horner.

Some plant-based metabolites like ergothioneine showed potential protective effects, while certain lipid-associated metabolites, including medium-chain fatty acids, appeared to have possible detrimental impacts on neurodevelopment.

First Trimester: A Critical Window for Intervention

The research revealed that early to mid-pregnancy may be a particularly sensitive window during which dietary influences most strongly impact child neurodevelopment. When comparing maternal blood samples from various pregnancy stages and childhood, only the pregnancy Western dietary pattern metabolite score from early-mid pregnancy consistently predicted neurodevelopmental outcomes.

“When comparing across cohorts, we observed the strongest associations in the first and second trimesters, suggesting that brain development during this period is particularly sensitive to maternal nutritional influences,” explains senior author Professor Morten Arendt Rasmussen from the University of Copenhagen.

The study also uncovered a complex interplay between genetic predisposition, maternal health, and dietary patterns. Children with higher genetic risk for neurodevelopmental disorders born to mothers with higher pre-pregnancy BMI showed the strongest associations with the Western dietary pattern. For ADHD diagnosis, this high-risk group had an odds ratio of 2.18 when exposed to a Western dietary pattern during pregnancy, while for autism diagnosis, the odds ratio jumped to a striking 4.59.

Rethinking Dietary Guidelines for Pregnancy

According to Dr. Horner, this study raises important questions about whether current dietary guidelines for pregnant women are sufficient.

“We know that nutritional demands increase during pregnancy, and our study highlights just how crucial dietary composition is for fetal development. While the Nordic diet is often considered healthy, our data show that many pregnant women follow dietary patterns that could be optimized to better support their child’s development. This study raises the question of whether existing dietary recommendations are sufficiently followed during pregnancy—and whether they have the desired impact on child health,” says Dr. Horner.

Dr. Horner adds: “Our analysis not only confirms a strong link between diet and ADHD risk but also identifies specific nutrients and foods that could serve as the foundation for improved dietary guidelines and preventative strategies. By understanding how maternal diet influences fetal development, we can better identify the key nutrients and dietary adjustments needed to reduce the risk of neurodevelopmental disorders. This opens new possibilities for refining dietary recommendations and promoting healthier outcomes for future generations.”